Spectrally resolved intraband transitions on two-step photon absorption in InGaAs/GaAs quantum dot solar cell

Two-step photon absorption processes in a self-organized In0.4Ga0.6As/GaAs quantum dot (QD) solar cell have been investigated by monitoring the mid-infrared (IR) photoinduced modulation of the external quantum efficiency (ΔEQE) at low temperature. The first step interband and the second step intraba...

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Bibliographic Details
Published in:Applied physics letters 2014-08, Vol.105 (7)
Main Authors: Tamaki, Ryo, Shoji, Yasushi, Okada, Yoshitaka, Miyano, Kenjiro
Format: Article
Language:English
Subjects:
ABSORPTION
Applied physics
BOUND STATE
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
EV RANGE
EXCITATION
Gallium arsenide
GALLIUM ARSENIDES
GROUND STATES
INDIUM COMPOUNDS
Indium gallium arsenides
LASER RADIATION
LAYERS
MODULATION
Photoexcitation
Photon absorption
PHOTONS
Photovoltaic cells
PULSES
QUANTUM DOTS
QUANTUM EFFICIENCY
REDUCTION
SOLAR CELLS
SPACERS
SPECTRA
TRAPS
VISIBLE RADIATION
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Summary:Two-step photon absorption processes in a self-organized In0.4Ga0.6As/GaAs quantum dot (QD) solar cell have been investigated by monitoring the mid-infrared (IR) photoinduced modulation of the external quantum efficiency (ΔEQE) at low temperature. The first step interband and the second step intraband transitions were both spectrally resolved by scanning photon energies of visible to near-IR CW light and mid-IR pulse lasers, respectively. A peak centered at 0.20 eV corresponding to the transition to virtual bound states and a band above 0.42 eV probably due to photoexcitation to GaAs continuum states were observed in ΔEQE spectra, when the interband transition was above 1.4 eV, directly exciting wetting layers or GaAs spacer layers. On the other hand, resonant excitation of the ground state of QDs at 1.35 eV resulted in a reduction of EQE. The sign of ΔEQE below 1.40 eV changed from negative to positive by increasing the excitation intensity of the interband transition. We ascribe this to the filling of higher energy trap states.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4893879